This invention relates, in general, to semiconductor products, and more particularly, to making semiconductor devices.
Generally, most very large scaled integrated (VLSI) semiconductor circuits are manufactured by depositing and patterning conductive and nonconductive materials or layers and by stacking the layers on top of each other. Patterning or creating features on or in a layer and then subsequently covering these features with an additional layer creates a nonplanar topography. As devices become more sophisticated and more complex, the number of layers stacked on each other tends to increase, and as the number of layers increases, planarity problems generally occur. Planarizing the stacked layers is a major problem, as well as a major expense in manufacturing semiconductor integrated circuits.
Generally, planarity problems are divided into two broad groups: local planarity, which is the planarity or the flatness of closely spaced features on a substrate and global planarity, which is planarity or flatness of all features over the substrate, regardless of their spacing and location. As the number of layers and the number of features increase, it is required that global planarity be achieved so that more features and more layers can be used. Planarization of features typically is attempted by several basic methods or approaches, such as using polymer planarization techniques with etching, using photolithography techniques with etching, combining both previously mentioned techniques, and chemical-mechanical polishing; none of which achieves global planarity.
Chemical-mechanical polishing has recently been used to planarize features. Successful use of chemical-mechanical polishing to planarize features would be a great benefit because of its relatively inexpensive cost compared to the previously discussed methods. Typically, the chemical-mechanical polishing method uses a pad and rubs the features that have to be planarized against the pad. Generally, a slurry is added while a rubbing action is taking place. The rubbing action of the features and the pad with the slurry creates a chemical-mechanical environment which removes or planarizes the features. However, several problems are evident with using chemical-mechanical polishing, such as inconsistency of removal rates across the substrate, variation of equipment parameters, and removal rates dependent on pattern density or location.
It can be seen that the conventional methods of planarizing and modifying features or topographies do not achieve global planarity, as well as being expensive and requiring additional processing steps. Each additional processing step and use of expensive equipment incur cost to a finished product. Additionally, each process step induces defects in the product. Therefore, a method and apparatus that would globally planarize features and substantially reduce the cost of building a product is highly desirable.